Laudator Temporis Acti

Bryan Ward-Perkins, The Fall of Rome and the End of Civilization (Oxford: Oxford University Press, 2006), pp. 118, 120 (notes omitted):

It may initially be hard to believe, but post-Roman Britain in fact sank to a level of economic complexity well below that of the pre-Roman Iron Age. Southern Britain, in the years before the Roman conquest of AD 43, was importing quantities of Gaulish wine and Gaulish pottery; it had its own native pottery industries with regional distribution of their wares; it even had native silver coinages, which may well have been used to facilitate exchange, as well as for purposes of prestige and gift-giving. The settlement pattern of later iron-age Britain also reflects emerging economic complexity, with substantial coastal settlements, like Hengistbury in modern Hampshire, which were at least partly dependent on trade. None of these features can be found reliably in fifth- and sixth-century post-Roman Britain. It is really only in about AD 700, three centuries after the disintegration of the Romano-British economy, that southern Britain crawled back to the level of economic complexity found in the pre-Roman Iron Age, with evidence of pots imported from the Continent, the first substantial and wheel-turned Anglo-Saxon pottery industry (at Ipswich), the striking of silver coins, and the emergence of coastal trading towns, such as Hamwic (Saxon Southampton) and London. All these features were new, or only just beginning, in around AD 700; but all had existed in southern Britain during the pre-Roman Iron Age.